To prove or disprove the assumption that certain metallic objects used at a crime scene were actually used by the suspect or victim, forensic scientists have developed several trace metal detection techniques. Recently, it has been suggested that 2-nitroso-1-napthol can be used as a spray reagent to form reactions with various trace metals that are visible without special viewing and photographic equipment. To fully investigate the potential of this reagent, several factors affecting the color and pattern formation were studied at a forensic laboratory at the University of Illinois. Results of the experiment indicated that a metal object must be held for approximately 1.5 minutes for satisfactory color and pattern formation to be observed. Metal ions transferred through a brief period of holding can be detected within 3 hours. Best results were obtained on individuals with high levels of perspiration. That more than one metallic object was held can be revealed if the objects are made of different metals or have distinct shapes or sizes. Tables, photographs, and six references are included. (Author abstract modified)